29 CFR 1605.1 -

In most cases whether or not a practice or belief is religious is not at issue. However, in those cases in which the issue does exist, the Commission will define religious practices to include moral or ethical beliefs as to what is right and wrong which are sincerely held with the strength of traditional religious views. This standard was developed in United States v. Seeger,380 U.S. 163 (1965) and Welsh v. United States,398 U.S. 333 (1970). The Commission has consistently applied this standard in its decisions. 1 The fact that no religious group espouses such beliefs or the fact that the religious group to which the individual professes to belong may not accept such belief will not determine whether the belief is a religious belief of the employee or prospective employee. The phrase “religious practice” as used in these Guidelines includes both religious observances and practices, as stated in section 701(j), 42 U.S.C. 2000e(j).